The histochemical and electron microscopic profiles of muscle spindles were analysed in gastrocnemius of adult rats,
@ES The muscle spindles showed the following characteristic features:
@EN 1, Extrafusal muscle fibers of lateral gastrocnemius muscle were composed with type II(type A, C) fibers and intrafusal muscle fibers were similar to type C fibers,
2. Although myonuclei of extrafusal muscle fibers were located in peripheral region, those of intrafusal muscle fibers were located on the center in equatorial regions and on the periphery in polar region,
3. According to the type of intrafusal muscle fibers, the shape and size of mitochondria were different,
4. Adjacent twin muscle spindles were observed,
5. Moderate activity of SDH was found in chain fibers and weak activity of phosphorylase was found in bag fibers,
Based on the present results, the correlation between extrafusal muscle fibers and intrafusal muscle fibers on fiber types was similar and the locations of nuclei, structures of capsules and mitochondria were different,
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